U.S. Pat. No. 6,358,254 to Anderson, the disclosure of which is incorporated by reference, describes spinal stenosis as a condition that inflicts millions of people with back and leg pain due to compression of spinal nerves. Severe cases often require surgery to relieve nerve compression and lessen the back and leg pain. A spinal laminectomy is the traditional operation performed to treat spinal stenosis. In this operation, the posterior aspects of the spinal column are removed to “unroof” the spinal canal and relieve the pressure on the nerves. Specifically, the spinous processes, lamina and portions of the facet joints are excised to relieve the nerve root compression.
Although a spinal laminectomy is often successful in relieving pressure on the nerves of the spinal canal, several disadvantages can be associated with the laminectomy. First, the laminectomy removes important sites of back muscle attachment which may lead to back muscle dysfunction and pain. Second, the laminectomy exposes the nerve sac which may cause scar tissue to form around the nerves, leading to recurrent pain. Third, the laminectomy can destabilize the spine resulting in a forward slippage of one vertebra on another, which can cause recurrent pain and deformity. Fourth, the laminectomy requires a large surgical exposure and significant blood loss, making the laminectomy less favorable for older patients. Finally, spinal stenosis can recur following the laminectomy, requiring revision surgery.
Laminectomy risks have led surgeons to seek an alternative for patients with severe spinal stenosis. Some surgeons have used multiple laminotomies to treat spinal stenosis. Laminotomies involve removing bone and soft tissue from the posterior aspect of the spine making “windows” into the spinal canal over areas of nerve compression. Multiple laminotomies remove less tissue than the laminectomy, resulting in less scarring, vertebral instability, and blood loss. However, laminotomies also have associated disadvantages. Laminotomies may not adequately relieve nerve compression and therefore the pain may not be fully abated. Moreover, laminotomies are more difficult to correctly perform than the laminectomy, and they still expose the nerves causing nerve scarring. Patients receiving multiple laminotomies also often have recurrent spinal stenosis requiring revision surgery.
For the foregoing reasons, there is a need for improved methods and devices for relieving the symptoms of spinal stenosis without the drawbacks of currently available techniques. More particularly, simple, safe, effective, and permanent methods and devices are needed to expand the spinal canal to relieve the pressure on the spinal nerves.